The present invention relates to stable lipophilic emulsions. More particularly, the present invention relates to stable lipophilic emulsions which may be stored and shipped for use with polymers comprised of acrylic and methacrylic acid, their alkyl esters and their alkyl amino alkyl esters for the coating of pharmaceutical dosage forms.
In the past, the coating of pharmaceutical dosage forms utilizing acrylic and methacrylic acid, their alkyl esters and their alkyl amino alkyl esters usually required the addition of talc to prevent the coating from being sticky and causing defects by tablets sticking to each other or the coating equipment. The sticking together of tablets and their separation causes deformities in the coating which are referred to in the art as “picks” when the pharmaceutical dosage forms such as tablets or capsules are separated.
More recently, in U.S. Pat. No. 5,292,522—Petereit et al. describe the usefulness of a lipophilic material to replace talc in the coating composition. Petereit et al. elaborate on this coating process in Petereit et al., “Glycerol Monostearate as a Glidant in Aqueous Film-Coating Formulations”, European Journal of Pharmaceutics and Biopharmaceutics, Volume 41, No. 4, pages 219-228 (1995). However, the coating method utilizing glycerol monostearate is difficult to practice due to the difficulty in preparing the lipophilic material for incorporation into the polymer emulsion. All of the examples disclosed by Petereit et al. disclose the preparation of a low solids emulsion of the lipophile, such as glycerol monostearate at 2%, at the time of coating. Also, preparation of the most useful dispersions use an emulsion stabilizer at about 40% of the lipophile. The emulsion stabilizer, a surface active ingredient, at this level may have an adverse effect on the permeability of the film. Further, since the lipophilic emulsion is not stable for periods more than several hours, the lipophilic emulsion must be prepared as a part of the process of coating the pharmaceutical dosage forms and this preparation requires heating of the ingredients, dispersing the ingredients and then cooling the dispersion before incorporation into the coating suspension. This is a cumbersome preparation process at the manufacturing and coating facility and this process of preparing the lipophilic emulsion during the coating process creates difficulties which manufacturers would like to avoid.